Electrophysiology is a specific domain of interventional cardiology where physicians use intra-cardiac catheters to locate and cure electrical dysfunctions of the heart rhythm, under X-Ray fluoroscopy guidance. A challenging electrophysiology procedure is radio-frequency ablation for the treatment of atrial fibrillation. Electrophysiologists need a special training to perfectly know the anatomy and the access pathways to all the sites of interest and some practice to select the correct devices and manipulate them to the desired target. The patient's anatomy can be recorded with 3D imaging devices, e.g. through CT or MRI, or by injecting contrast agent locally just at the beginning of the intervention, e.g. into the left atrium and ostium of the pulmonary veins for atrial fibrillation or into coronary veins and sinus for a cardiac resynchronization therapy. The physician basically has to perform a mental registration to navigate in the live fluoro images where the structural information is not visible anymore. For atrial fibrillation procedures, knowing the exact positions of the catheters when measuring electrical potentials is the key to find the sources that cause fibrillation, e.g. the ectopic foci or the reentry loop. Even more important is an anatomical mapping of the ablation sites in order to perform the desired ablation patterns, such as pulmonary vein isolation or roof line ablation in the left atrium.
Tracking a third-party object like an interventional tool or a visible anatomical landmark is mandatory in interventional X-ray if one wants to compensate the motion of an anatomy of interest, e.g. a heart chamber or the coronary sinus, if said organ is mostly invisible.
However, the relationship between the motion of a tracked intervention device and the part of the anatomy that is interesting for electrophysilogic intervention may be complex. In the chest area, for example, the motion of an intervention device is mostly induced by two factors, the heart beat and the breathing motion.
Since in the chest area these two distinct motion sources effect their surrounding differently, it may be considered necessary to separate these motion sources
Known measures for the separation of different motion sources, which motion sources produce motions with distinct frequency bands, are based on filtering the overall motion of the tracked objects to recover the motion originating from either one of the source. However, filtering may result in lags that alter the quality of the motion compensation. Furthermore, the outcome of filtering may degrade quickly when the image rate of the fluoroscopy drops down.
Another known measure consists of using a temporal model of one (or several) of the motion sources. The temporal model(s) is (are) then fitted to the recorded motion. This may not be very flexible for coping with a huge motion variability, e.g. arrythmia of the cardiac or breathing motion.